Cold rolling metal



Sept. 13, 1932. w. c. CORYELL COLD ROLLING METAL Filed July 19, 1950 UAWTL.

well as one.

Patented Sept. 13, 1932 UNITED STATES PATENT ormca WILLIAI O. COB-LL, OE YOUNGSTOWN, OHIO, AS SIGNOB TO REPUBLIC STEEL CORPO- RATION, 01". YOUNGSTOWN, OHIO,

A. CORPORATION OF NEW JERSEY COLD ROLLING METAL Applicationjled July 18, 1930. Serial No. 489,203.

The present invention relates to the art of cold rolling metal in the form of strip or sheets, out of previously hot rolled material. For convenience, the pieces worked upon will be described as strip but it must be kept/in mind that the invention is applicable to both sheets and strip. I

In general the method consists in preparing a hard piece of metal strip for rolling by providing it with a soft end. Thesoft end may be produced in different ways. Thus, the end of the hard strip may be annealed to soften it. A am, a softer or more ductile material may e welded to the end of the hard piece. I

Obviously both ends of the hard material strip may be provided with soft material, as Whether one or both ends be made soft depends upon the circumstances in a particular case.

One advantage of the soft end in associa-' I tionwitha strip body of hard material is in cushioning the blows of thereducing rolls of the mill through which the strip passes.

Without soft material at the ends of a hard. strip the rolls will often fall with heavy.

blows upon their bearings as they leave the ends of the hard material. Such heavy blows produce objectionable stresses and strains in the mill parts and necessarily greatly reduce the lives of the parts.

Another advantage of the soft end is the prevention of tail marks; Due to the drawn out and irregular ends which are formed on cold rolled hard strip, the pressure of the rolls as they engage these ends of limited area between them often cause tail marks in the roll surfaces that require roll replacements with the incident expense and loss of time as well as extra work ingrindiug out the marks. Bythe use of my invention such injury to the rolls is prevented. Where both ends of the strip are soft there is an easy entrance of the strip into the mill pass as well as an easy exit. a ,I

The nature and advantages of my invention will be more fully understood upon reference to the following detailed description takenin connection with the accompanying drawing while the scope of the invention will extremity of the strip; lar elevation of the soft end of a strip tapered be particularly pointed out in the appended claims.

In said drawing, tion of a hard metal strip provided with soft ends in accordance with the present invention; Fig. 2 is a similar elevation representmg the same piece after it has gone through one pass of a reducing mill; Fig. 3 is a similar view illustrating the stri after it has gone through a-second pass; Fig. 4'is a similar view illustrating the stri after it has gone through a third pass; li ewise, Figs. 5 and 6 are similar views illustrating the strip after it has gone throu h fourth and fifth passes, respectively; Fig. is a similar view illustratofl F1 8 is a side elevation of one end of a modified strip wherein-the end is composed of portions increasing in softness toward the and Fig. 9 is a simiso as-to more easily'enter the pass of the mill on the initial rolling. Throughout these views like characters refer to like parts.

The figures'of the drawin are diagrammatic representations in whic the thickness Fig. 1 is an edge eleva the finished strip with thesoft ends cut is greatly magnified while the length is great- 1y reduced. Thus the thickness shown may be four or five times the actual thickness of the piece and the lengths indicated will be in-each instance about one two hundredth of the actual length. These views merely show thickness and length and the hard portions are indicated by the letter H without and With exponents and the soft portions by the lettersSwithout and with exponents. Intel-mediate portions shown in the modification of Fig. 8 are indicated by the letters LIH and MS, the former indicating medium hardness and the latter, medium softness. Of course, all these terms are relative.

The material as it comes from the hot mill is. in the form of a strip having a flat wide section and considerable length. The thickness is rather uniform throughout the length of the piece but not absolutely so. Such a piece may be the portion H of the strip shown in Fig. 1, to the ends of which the soft ends S, S are welded, or it may be the entlre piece -tions equal or tion H and the end portions S, S, before the latter are made soft by annealing. Usually it is preferable to take a hard strip and weld the soft ends to it as welding is a compararolling; H and S, the corresponding parts after the strip has gone through one pass of the mill; H and S the corresponding parts after the strip has gone through the second tively economical operation but'in some inpass of the mill; H and S the correspondstances it may be preferable to soften the ends by annealing. Dash lines in the several figures show generally where the metal changes from one degree of hardness or softness to another. Of course, actually, quite a zone may be occupied with the metal which intervenes between the hard body and a soft end or between a portion of one hardness and a neighboring portion of less hardness, as indicated in Fig. 8, but the dash lines are not intended to indicate more than the general region of change.

When the piece has been provided with the soft ends then it is ready to roll. Figs. 2 to -6 inclusive represent the piece after it has passed through the first, second, third, fourth, and fifth passes of the mill, respec tively. In the assumed case the soft ends are reduced 25% per pass and the intermediate hard portion H 20% per pass. Of course, these are merely illustrative figures and obviously the amount of reduction would ordinarily not be the same in each pass as there would be no necessity for. having the reducfor adjusting the rolls with that precision. However, what is stated will show that as the strip is passed through a properly adjusted mill it will be gradually reduced in thickness, the soft ends S being reduced more rapidly than the hard portion constituting the main body of the strip. Thus the end taper will be preserved.

In these rollings there will be a variable thickness at the extreme ends of the pieces as well as the points where the hard and soft metals join. The thickness at the ends becomes truncated or tapered and likewise at the joints it will vary from the thickness of the soft portion at one end of the joint to the thickness of the hard portion at its other end. The ends and joints become points of variable thickness and the oints are in reality tapered shoulders. They will vary in shape according to the relative hardness and softness of the strip and strip ends, the amount of reduction for which the mill rolls have been set, the diameter of the rolls and o her factors. The ends and shoulders shown are therefore merely typical and illustrative and are not intended to be exact representations. The same is true of the squared ends of the soft portions. They, in most instances, represent the ends after the piece has been rolled, although the ends after rolling are usually drawn out into irregular shapes. However, if the ends are sheared off for squaring up, as they sometimes are, they will in most cases be entered into the mill as squared ends.

In the drawing, H and S represent the hard and soft portions of the strip. before rolling to put taper those ends before starting the strip ing parts after the. strip has gone through the third pass of the mill; H and S*, the corresponding parts after the strip has gone through the fourth pass of the mill; and H and S the corresponding'parts after the strip has gone through the fifth pass of the mill. In these variously reduced strips are the joints or shoulders J5 J J J and J In the final form of the hard strip, shown in Fig. 7 the ends S have been removed by severing the strip at the joints J and leaving the resulting hard strip H Obviously, instead of having a strip provided with two soft ends it might be desirable in some instances to employ a strip having one soft end. However, in ordinary rolling it is preferable to have both ends soft. The advantage of this arrangement is the more gentle entering and leaving of the piece as it passes through the mill. It is well known that all the stressed parts of a mill, such as the housings, screws, and roll-necks, each have more or less elasticity which is called into play when the piece enters intothe mill. In the old art a hard piece enters the pass too abruptly and thereby brings excessive pressure upon the localized entering edge of the piece. But, by the employment of the soft end, the piece enters less abruptly into all passes rather as a tapered end of varying thickness. The length of the taper depends upon many variables but I have found it to Y be plainly several inches and I know of no reason why it may not under some conditions extend, in an extremely small degree, throughout a considerable length of the rolled strip.

In some instances when I require an exceptionally easy discharge of the piece from the pass, I stop the mill just before the end leaves. I then start the mill again. The slow starting speed of the mill, at the instant the piece leaves the mill, gives an extremely easy seating of the rolls in line and line contact.

In this connection it may be well to refer to the modification shown in Fig. 8 wherein I have shown a gradient in hardness from the soft end S to the hard main portion H, such gradient including the medium soft portion MS and the medium hard portion MH. Preferably the portions S, MS and MH are welded together and then to the end of the hard strip H in the manner illustrated. With this gradient in hardness it will be obvious that as the strip is rolled the end thus constituted will assume a more wedgelike taper than if it were composed only of one soft piece. Insteadwf relying upon the taper in the soft ends I may through the mill, as indicated in Fig. 9 wherethe soft end S is provided with a slight taper. With this tapered end to begin with, therolls will be gradually separated by the entrance of the strip in the initial pass as well as in later passes. With the tapered end S trailing, the rolls will be allowed to gradually approach each other as the end of the strip, leaves the pass.

In all of these cases of rolling, the rolls will be separated from a line to line contact previous to their engaging the hard portion of the piece entering into the pass. During this preliminary travel of the strip there will be a very appreciable angular rotation of the rolls. During such rotation the advancing soft end of the strip acts upon the rolls after the manner of a wedge and separates them to an extent where they readily receive the hard portion of the strip. Sim- 1larly, when the strip is about to leave the pass, the soft end allows the rolls to gradually approach each other until they come into line to line contact which is their position when idle. All this action of the strip prevents rough handling of the rolls with the consequent evil'effects. Among the latter are the enormous blows which occur when a strip of hard material passes from the mill, as would occur were the hard material not provided with a soft end as contemplated by the present invention. The force of such a blow at first blush may" seem unimportant, but an example will show ow serious a matter it is. Thus, suppose there is a million pounds pressure of the rolls upon the piece and the piece is .060 inches thick, then the blow based on stress and distance expressed in tons feet is not employed. But when it is employed then the heavy blows of the prior practice are avoided.

Another advantage of the invention lies in the greater uniformity of applying the rolling pressure to the surface of the rolls. When rolling a hard piece of metal the ends of the piece do not extend out into so long a taper as they do when rolling a soft piece of metal. Moreover the ends become lrregularly formed. When so formed the leading point must therefore enter first and the most extended points leave last. These points therefore cause a localized and excessive pressure at the points where they engage the rolls, and in spite of the rolls having a very hard surface and tough interior, the surface may receive from such points what are called tail marks. The more extended the taper the less the tendency exists to tail-mark the roll. When a tail mark is once made, the roll has to be ground so as to grind it out. If the mark is deep then the material of the roll surface will be damaged still more and in the case of such serious tail marks it may be necessary to move the material of the roll from the depth of twenty or thirty thousandths of an inch. Or, again, the roll may be damaged beyond the depth of its hard rolling surface. case it is of little value, until rehardening and regrinding. It has been at best greatly damaged.

What I claim as new and desire to secure by a patent of the United States is: I 1. The method of rolling metal strip which consists in providing a piece of strip having its main portion relatively hard and an end which is relatively soft, completely passing said strip through mill reducing passes a plurality of times, and after the rolling is completed cutting off said soft end to leave a reduced hard rolled strip.

2. The method of rolling metal strip which consists in providing a piece of strip to be rolled having a relatively hard main portion and relatively soft ends, setting the mill rolls.

for a reduction, and passing said strip completely through the pass between said rolls, the soft ends cushioning the rolls both at the entrance of the strip into the pass and at its exit therefrom.

3. The method of rolling metal strip which consists in providing a p1ece of strip to be rolled having a relatively hard main portion and relatively soft ends, setting the mill rolls for a reduction, pasing said strip completely through the pass between said rolls to obtain the reduction in the strip corresponding to that for which said rolls were set, the soft ends cushioning the rolls as they pass between them, and after the rolling is completed cutting off the soft ends to leave a reduced hard rolled strip.

4. The method of rolling metal strip which consists in providing a piece of strip having its main portion relatively hard and an end which is relatively soft, passing said strip completely through one of the passes of said mill, and thereafter cutting off said soft end to leave a reduced hard rolled strip.

WILLIAM C. CORYELL.

In such 

